From: Miklos Szeredi mszeredi@redhat.com
[ Upstream commit e1e71c168813564be0f6ea3d6740a059ca42d177 ]
There is a potential race between fuse_read_interrupt() and fuse_request_end().
TASK1 in fuse_read_interrupt(): delete req->intr_entry (while holding fiq->lock)
TASK2 in fuse_request_end(): req->intr_entry is empty -> skip fiq->lock wake up TASK3
TASK3 request is freed
TASK1 in fuse_read_interrupt(): dereference req->in.h.unique ***BAM***
Fix by always grabbing fiq->lock if the request was ever interrupted (FR_INTERRUPTED set) thereby serializing with concurrent fuse_read_interrupt() calls.
FR_INTERRUPTED is set before the request is queued on fiq->interrupts. Dequeing the request is done with list_del_init() but FR_INTERRUPTED is not cleared in this case.
Reported-by: lijiazi lijiazi@xiaomi.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/fuse/dev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index b8d58aa08206..339ebd3ab4f2 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -288,10 +288,10 @@ void fuse_request_end(struct fuse_req *req)
/* * test_and_set_bit() implies smp_mb() between bit - * changing and below intr_entry check. Pairs with + * changing and below FR_INTERRUPTED check. Pairs with * smp_mb() from queue_interrupt(). */ - if (!list_empty(&req->intr_entry)) { + if (test_bit(FR_INTERRUPTED, &req->flags)) { spin_lock(&fiq->lock); list_del_init(&req->intr_entry); spin_unlock(&fiq->lock);